Chapter 14: Quality of Service
174
Section II: Advanced Operations
Policy
Component
Hierarchy
The purpose of this example is to illustrate the hierarchy of the
components of a QoS policy and how that hierarchy needs to be taken into
account when assigning new priority and DSCP values. A new priority can
be set at the flow group and traffic class levels, while a new DSCP value
can be set at all three levels—flow group, traffic class and policy. The
basic rules are:
A new setting in a flow group takes precedence over a corresponding
setting in a traffic class or policy.
A new setting in a traffic class takes precedence over a corresponding
setting in a policy.
A new setting in a policy is used only if there is no corresponding
setting in a flow group or traffic class.
This concept is illustrated in Figure 17 on page 175. It shows a policy for a
series of traffic flows consisting of subnets defined by their destination IP
addresses. New DSCP values for the traffic flows are established at
different levels within the policy.
Traffic flows 149.11.11.0 and 149.22.22.0, defined by classifiers 1 and 2,
are attached to a flow group, traffic class, and policy that contain new
DSCP values. Because a setting in a flow group takes precedence over
that of a traffic class or policy, the value in the flow group is used. The
result is that the DSCP value in the two traffic flows is changed to 10.
The flow group for traffic flows 149.33.33.0 and 149.44.44.0, defined in
classifiers 3 and 4, does not contain a new DSCP value. Therefore, the
new value in the traffic class is used, in this case 30. The policy also has a
DSCP setting, but it is not used for these traffic flows because a new
DSCP setting in a traffic class takes precedence over that of a policy.
Finally, the new DSCP value for traffic flows 149.55.55.0 and 149.66.66.0,
defined in classifiers 5 and 6, is set at the policy level to a value of 55
because the flow group and traffic class do not specify a new value.
Summary of Contents for AT-S63
Page 14: ...Figures 14 ...
Page 18: ...Tables 18 ...
Page 28: ...28 Section I Basic Operations ...
Page 58: ...Chapter 1 Overview 58 ...
Page 76: ...Chapter 2 AT 9400Ts Stacks 76 Section I Basic Operations ...
Page 96: ...Chapter 5 MAC Address Table 96 Section I Basic Operations ...
Page 114: ...Chapter 8 Port Mirror 114 Section I Basic Operations ...
Page 116: ...116 Section II Advanced Operations ...
Page 146: ...Chapter 12 Access Control Lists 146 Section II Advanced Operations ...
Page 176: ...Chapter 14 Quality of Service 176 Section II Advanced Operations ...
Page 196: ...196 Section III Snooping Protocols ...
Page 204: ...Chapter 18 Multicast Listener Discovery Snooping 204 Section III Snooping Protocols ...
Page 216: ...Chapter 20 Ethernet Protection Switching Ring Snooping 216 Section III Snooping Protocols ...
Page 218: ...218 Section IV SNMPv3 ...
Page 234: ...234 Section V Spanning Tree Protocols ...
Page 268: ...268 Section VI Virtual LANs ...
Page 306: ...Chapter 27 Protected Ports VLANs 306 Section VI Virtual LANs ...
Page 320: ...320 Section VII Internet Protocol Routing ...
Page 360: ...Chapter 30 BOOTP Relay Agent 360 Section VII Routing ...
Page 370: ...Chapter 31 Virtual Router Redundancy Protocol 370 Section VII Routing ...
Page 372: ...372 Section VIII Port Security ...
Page 402: ...Chapter 33 802 1x Port based Network Access Control 402 Section VIII Port Security ...
Page 404: ...404 Section IX Management Security ...
Page 436: ...Chapter 36 PKI Certificates and SSL 436 Section IX Management Security ...
Page 454: ...Chapter 38 TACACS and RADIUS Protocols 454 Section IX Management Security ...
Page 462: ...Chapter 39 Management Access Control List 462 Section IX Management Security ...
Page 532: ...Appendix D MIB Objects 532 ...